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copied!<p>The well-known <a href="http://cr.yp.to/docs/selfpipe.html" rel="noreferrer">self-pipe trick</a> can be <a href="http://lkml.org/lkml/2006/7/10/300" rel="noreferrer">adapted</a> for this purpose.</p> <pre><code>#include <errno.h> #include <fcntl.h> #include <stdio.h> #include <string.h> #include <sys/wait.h> #include <sysexits.h> #include <unistd.h> int main(int argc, char **argv) { int pipefds[2]; int count, err; pid_t child; if (pipe(pipefds)) { perror("pipe"); return EX_OSERR; } if (fcntl(pipefds[1], F_SETFD, fcntl(pipefds[1], F_GETFD) | FD_CLOEXEC)) { perror("fcntl"); return EX_OSERR; } switch (child = fork()) { case -1: perror("fork"); return EX_OSERR; case 0: close(pipefds[0]); execvp(argv[1], argv + 1); write(pipefds[1], &errno, sizeof(int)); _exit(0); default: close(pipefds[1]); while ((count = read(pipefds[0], &err, sizeof(errno))) == -1) if (errno != EAGAIN && errno != EINTR) break; if (count) { fprintf(stderr, "child's execvp: %s\n", strerror(err)); return EX_UNAVAILABLE; } close(pipefds[0]); puts("waiting for child..."); while (waitpid(child, &err, 0) == -1) if (errno != EINTR) { perror("waitpid"); return EX_SOFTWARE; } if (WIFEXITED(err)) printf("child exited with %d\n", WEXITSTATUS(err)); else if (WIFSIGNALED(err)) printf("child killed by %d\n", WTERMSIG(err)); } return err; } </code></pre> <p>Here's a complete program.</p> <pre> $ ./a.out foo child's execvp: No such file or directory $ (sleep 1 && killall -QUIT sleep &); ./a.out sleep 60 waiting for child... child killed by 3 $ ./a.out true waiting for child... child exited with 0 </pre> <p>How this works:</p> <p>Create a pipe, and make the write endpoint <code>CLOEXEC</code>: it auto-closes when an <code>exec</code> is successfully performed.</p> <p>In the child, try to <code>exec</code>. If it succeeds, we no longer have control, but the pipe is closed. If it fails, write the failure code to the pipe and exit.</p> <p>In the parent, try to read from the other pipe endpoint. If <code>read</code> returns zero, then the pipe was closed and the child must have <code>exec</code> successfully. If <code>read</code> returns data, it's the failure code that our child wrote.</p>

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